Modern commercial aircraft typically include a stall warning system which is triggered by the angle of attack of the aircraft as determined by an angle of attack vane. Such aircraft also include an integrated airspeed control command and display system which aids a pilot during take-off, climb out, let down, approach, landing and go-around maneuvers. Such integrated systems are also based on various parameters relating to flight conditions including the aircraft's angle of attack as determined by an angle of attack vane or the like.
It is customary to locate the angle of attack vane on the sides of an aircraft's fuselage. However, these side mountings may lead to problems when the aircraft is in a banked turn or flown in a yawed flight. Under such conditions, i.e. when an aircraft is in a banked turn or flown in a yawed condition, the position of the angle of attack sensing vane will be determined by the local airflow passing the vane. The angle of attack vanes are usually located so that the changes in the local airflow at the vane cause the vane to pivot in accordance with the angle of attack. The local airflow at these fuselage locations are determined to a lesser extent by the yaw of the aircraft so that the indicated angle of attack is actually a function of both the angle of attack and the yaw.
One approach for avoiding yaw induced problems is disclosed in my earlier patent for an aircraft control system, as disclosed in my U.S. Pat. No. 5,590,853. As disclosed therein, an aircraft control system computes a yaw compensated angle of attack. The system includes an angle of attack sensor for generating a signal which represents an aircraft's angle of attack as determined by an angle of attack vane and a transverse accelerometer for generating a signal in response to the lateral acceleration of the aircraft. A summing device sums the two signals to thereby provide a yaw compensated angle of attack signal.
All aircraft produce wake vortices like two small horizontal tornadoes trailing behind the wingtips. The larger and heavier the plane the stronger the wake. These vortices result from the outflow and uplift of air around the wingtip of an aircraft and have a relationship to a wing's lift. Accordingly, it is believed that measuring the airflow angle at the wingtip, referred to hereinafter as the vortex angle may provide more accurate information than a conventional angle of attack system.
Accordingly, it is presently believed that there may be a commercial market for an airflow system to measure the vortex angle. There should be a commercial market for a system in accordance with the present invention because it is believed that such system will reduce or eliminate problems associated with banked turns and yaw particularly during landings and provide a more accurate indication of the vortex angle as the plane banks and turns.
Further, the systems in accordance with the present invention should be less likely to be physically damaged when a plane is being served or worked on. Such systems will also be accessible and readily replaced in the event of damage, are durable and can be produced and installed at a reasonable cost.